The cellulolytic system of Talaromyces emersonii

Abstract

Talaromyces emersonii, a thermophyllic fungus was grown on cellulose/corn steep liquor/NH₄NO₃ medium. The kinetics of growth and extracellular cellulase production were measured. The enzyme system was found to be comprised of four to five forms of exo-β-1,4-glucanase (cellobiohydrolase; 1,4-β-d-glucan cellobiohydrolase, EC 3.2.1.91), at least two forms of endo-1,4-β-glucanase (1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4) and three enzymes exhibiting β-glucosidase (cellobiase; β-d-glucoside glucohydrolase, EC 3.2.1.21) activity. One of the latter, termed β-glucosidase III, is induced concurrently with the cellulases but disappears from the medium because of the low pH that develops during growth. The cellulases by contrast are more acid-stable. Later in the growth cycle a second from of β-glucosidase, termed β-glucosidase I, accumulates. An intracellular β-glucosidase, β-glucosidase IV, was also detected. The possible functions of these enzymes are discussed.